<template>
  <div class="pagination">
    <button v-if="pageNo != 1" @click="$emit('getPage',pageNo - 1)">上一页</button>
    <button v-if="pageNum.start != 1" @click="$emit('getPage',1)">1</button>
    <button v-if="pageNum.start > 2">···</button>

    <button v-for="(page,index) in pageNum.end" :key="index" v-if="page >= pageNum.start" @click="$emit('getPage',page)" :class="{active:pageNo == page}">{{page}}</button>

    <button v-if="pageNum.end < totalPage-1">···</button>
    <button v-if="pageNum.end != totalPage" @click="$emit('getPage',totalPage)">{{totalPage}}</button>
    <button v-if="pageNo != totalPage" @click="$emit('getPage',pageNo + 1)">下一页</button>

    <button style="margin-left: 30px">共 {{total}} 条</button>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props:['pageNo','pageSize','total','continues'],
  computed:{
    // 一共多少页
    totalPage() {
      return Math.ceil(this.total/this.pageSize);
    },
    // 计算出连续页码的起使数据和结束数据
    pageNum() {
      // 先定义两个变量存储起使数字和结束数字
      let start = 0 , end = 0;
      // 连续页码数字5【就是至少5页】
      if(this.continues > this.totalPage) {
        // 不正常现象，总页数没有连续页码多
        start = 1
        end = this.totalPage
      } else {
        // start = this.pageNo < Math.ceil(this.continues/2) ? 1 : this.pageNo - parseInt(this.continues/2)
        // end = this.pageNo > this.totalPage - parseInt(this.continues/2) ? this.totalPage : this.pageNo + parseInt(this.continues/2)
        if(this.pageNo < Math.ceil(this.continues/2)) {
          start = 1
          end = this.continues
        } else if(this.pageNo > this.totalPage - parseInt(this.continues/2)) {
          start = this.totalPage - this.continues + 1
          end = this.totalPage
        } else {
          start = this.pageNo - parseInt(this.continues/2)
          end = this.pageNo + parseInt(this.continues/2)
        }
      }
      return {start,end}
    }
  },
};
</script>

<style lang="less" scoped>
.pagination {
    text-align: center;
  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: #606266;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #409eff;
      color: #fff;
    }
    &:hover {
      background: skyblue;
    }
  }
}
</style>
